The invention relates to a tape head system and to a method for operating a tape head system.
In modern tape systems, data is organized in data tracks which are written and read back in a parallel fashion by a read and write head comprising servo read, data read and data write elements, i.e., transducer elements. These data tracks run in the longitudinal direction of the magnetic tape and are much narrower than the excursions the magnetic tape experiences in the lateral direction as a result of imperfections in the mechanical entrainment system. Therefore, it is crucial to accurately position the head relative to the magnetic tape in the lateral direction, and to maintain this relative position as the magnetic tape is streamed. To this end, as well as for other purposes, media manufacturers write servo tracks on the magnetic tape parallel to and interleaved with the data tracks. The servo read elements read the servo information stored in the servo tracks, which is then used for aligning the head with the data tracks on the magnetic tape.
Servo tracks are typically written to the magnetic tape using one servo write element for each servo track. Each servo write element generally comprises a yoke having one or more gaps and a coil for producing a magnetic field at each gap. The write elements are configured to imprint a specific pattern on the magnetic tape via fringing magnetic fields. This pattern contains the information required to determine the instantaneous lateral location of the data read and write elements (or the head as a whole) using a timing-based-servo (TBS) scheme as for example described in EP 0 690 442 A2.
TBS is a technology that was developed specifically for linear tape drives. It has been adopted by the Linear Tape Open (LTO) Consortium as a standard for the so-called LTO tape drive systems. In TBS systems, servo patterns generally comprise chevron shapes, having magnetic transitions with two different azimuthal slopes. An estimate of the head position is derived from the relative timing of pulses (also known as di-bits) generated by the read element reading the servo pattern.
Generally speaking, the magnetic tape should be in close contact with the servo write element to ensure a high-quality servo pattern being imprinted during writing. When the magnetic tape is run across the servo write head, an air bearing layer forms (air being trapped between the magnetic tape and the servo write head). Current servo write heads use one or more sharp edges to skive off the air. A small low pressure pocket forms behind the skiving edge, and atmospheric pressure then pushes the magnetic tape into contact with the servo write head.